Method for Processing an Uplink Grant of Which a Resource Size Is Zero in Wireless Communication System and a Device Therefor

1. A method for a user equipment (UE) operating in a wireless communication system, the method comprising: transmitting uplink data; receiving uplink grant after the uplink data is transmitted; considering that the uplink data transmission is performed successfully, if a resource size of the uplink grant is ‘zero;’ performing a Hybrid-ARQ (HARQ) process of the uplink data as successful uplink transmission; and setting a HARQ feedback value of the HARQ process to ‘ACK,’ wherein the setting of the resource size of the uplink grant to ‘zero’ includes a transport block size of the uplink grant is set to zero.

2. The method according to claim 1 , wherein when the UE receives the uplink grant of which the resource size is zero, the UE doesn't generate a MAC PDU for the uplink grant.

3. The method according to claim 2 , wherein the UE doesn't generate a MAC PDU for the uplink grant even if there is a data available for transmission.

4. The method according to claim 1 , wherein the UE transmits a buffer status reporting of which a buffer size is set to zero with the uplink data.

5. A User Equipment (UE) for operating in a wireless communication system, the UE comprising: a Radio Frequency (RF) module; and a processor operably coupled with the RF module and configured to: transmit uplink data; receive uplink grant after the uplink data is transmitted; consider that the uplink data transmission is performed successfully, if a resource size of the uplink grant is ‘zero;’ perform a Hybrid-ARQ (HARQ) process of the uplink data as successful uplink transmission; set a HARQ feedback value of the HARQ process to ‘ACK,’ wherein the setting of the resource size of the uplink grant to ‘zero’ includes that a transport block size of the uplink grant is set to zero.

6. The UE according to claim 5 , wherein when the processor receives the uplink grant of which the resource size is zero, the UE doesn't generate a MAC PDU for the uplink grant.

7. The UE according to claim 6 , wherein the processor doesn't generate a MAC PDU for the uplink grant even if there is a data available for transmission.

8. The UE according to claim 5 , wherein the processor transmits a buffer status reporting of which a buffer size is set to zero with the uplink data.